The goal of this study is to find out the optimal luminance and color temperature of front light for reflective displays in
different ambient illumination by conducting series of psychophysical experiments. A color and brightness tunable front
light device with ten LED units was built and been calibrated to present 256 luminance levels and 13 different color
temperature at fixed luminance of 200 cd/m<sup>2</sup>. The experiment results revealed the best luminance and color temperature
settings for human observers under different ambient illuminant, which could also assist the e-paper manufacturers to
design front light device, and present the best image quality on reflective displays. Furthermore, a similar experiment
procedure was conducted by utilizing new flexible e-signage display developed by ITRI and an optimal front light device
for the new display panel has been designed and utilized.
Most of high-contrast images are common with dark and bright area. It is difficult to present the detail on both dark and
high light areas on display devices. In order to resolve this problem, we proposed a method of image enhancement to
improve this image quality and used bilateral filter to keep the detail.
In paper, we applied an appropriate algorithm to process images. At first, we use bilateral filter to separate image. One is
large scale image and the other is detail image.
Second, we made large scale image which was translated into histogram. In order to make the images divided into three
stairs, such as lightness, middle-tone and darkness region. We decided two optimal threshold parameters. Finally,
according to three images we use different tone-mapping method to process each stair. The tone-mapping method
includes adaptive s-curve and gamma curve algorithms.
The experiment results of this study revealed image detail and enhancement. To avoid contour phenomenon is in